Inductive output tubes are used particularly as the final amplification stage for a radio frequency signal, the output from the tube being connected to a transmission antenna. These tubes transfer high electrical powers and their efficiency is typically of the order of 50%. Due to this efficiency, there is a large amount of emitted heat that has to be dissipated.
Heat is emitted particularly in a tube collector. The collector forms one of the ends of the tube and receives the electrons emitted by an electron gun at the other end of the tube. Electrons interact with cavities, on their path between the electron gun and the collector. This interaction amplifies a radio frequency signal. When the electrons bombard the collector, they still have a high amount of energy that increases the temperature of the collector. The collector can be cooled using a hydraulic circuit by circulating a heat transporting fluid, for example water, inside the collector. For example, the hydraulic circuit may include a fluid-air exchanger located outside a building in which the tube is located. The heat transported by the heat transporting fluid is then carried outside the building into the ambient air.
To make sure that operation is possible under all circumstances and particularly when the ambient temperature is below 0° Celsius, an anti-freeze product, for example containing glycol, is added to the water in the heat transporting fluid.
Some collectors used particularly in inductive output tubes are said to be vacuum collectors. More precisely, this type of collector comprises several electrodes that are at different potentials up to several kilovolts. This type of collector can increase the efficiency of the electron tube in which it is installed. Nevertheless, the collector has to be cooled. If the cooling means described above are used, it is necessary to use a particular anti-freeze product with a high resistivity to avoid creating a medium along which an electric current can pass between the different electrodes of the collector. This particular anti-freeze product is much more expensive than more conventional products, for example like those used in the cooling circuit of an automobile vehicle.